184 
POPULAR SCIENCE EEYIEW. 
papers. — Dr. Sclmitzlein died on October 24, 1868, at the age of fifty-five, 
lie had suffered for upwards of four months from an accident which he met 
with while botanising on the Tyrol. He was Professor of Botany at Er- 
langen, and director of the Botanic Garden. His chief work is the ^^Illus- 
trations of the Natural Families of Plants ” {Iconographia Fumiliarum 
Natw'alium Regni Vegetahilis), which, unfortunatel}’’, is not completed. 
The Colon r-reactio7is of Lichens. — It has recently been asserted by the Bev. 
Mr. Leighton and by Herr Dr. Nylander that the chemical reactions of 
lichens afford a clue to their specific qualities. This assertion, however, 
receives very distinct denial from Dr. Lauder Lindsay, who has given con- 
siderable attention to the subject. The various experiments conducted by Dr. 
Lindsay lead him to the following conclusions : — 1. The same specimen, in 
the hands of the same operator, in its difterent parts, at different times, fre- 
quently exhibits colour-reactions different at least in degree. 2. The same 
species, in the hands of the same operator, and, still more so, in those of 
different experimenters, in different specimens from the same ©r different 
localities, differing in freshness of collection or age, occurring in different 
varieties of forms, or in different conditions of growth (fertile or sterile, 
hypertrophied or degenerated), frequently shows colour-reactions differing 
equally in kind and degree. 3. Colorific quality is determined by circum- 
stances (not fully understood) connected with («) locality of gTOwth in rela- 
tion to climatic, geographical, topographical, geological, or other conditions. 
(h) States of development, in relation to sterility, hypertrophy, or degene- 
ration of the vegetable tissues proper. 4. This inconstancy of colorific 
property leads the archil manufacturer never to depend on laboratory 
testings in the purchase of his orchella weed,” or in determining its 
commercial value j for it not unfrequently happens that a most promising 
Roccella even proves worthless, and is, as such, cast aside. 5. Colour- 
reaction, though interesting in itself in connection with the general subject 
of lichen colorific or colouring matters, affords no aid that can he depended 
on, either (a) to the systematist in defining species, or (6) to the dye manu- 
facturer in determining the value of his ‘^orchella weed.” — Scientific 
Opinion, March 3. 
How to Bleach Wood Pulp. — This is a question of some importance in re- 
lation to the manufacture of a certain form of paper, and it is answered by a 
French chemist in a paper in a recent number of the Rcmie de Chimie, which 
appears in abstract in the Journal of the Society of Arts. M. Ouvli states that 
chloride of lime, if it happens to be in the slightest excess, has a tendency 
to give a yellow tinge to the pulp ; that all energetic acids, without 
exception, tend to give a reddish colour to the paper when exposed for a 
long time to the effects of the sun or of moisture, and that the least trace of 
iron is sufficient in a very short time to blacken the pulp. He says he has 
succeeded in avoiding all these inconveniences by the use of the following 
mixture : — For a liundredweight of wood-pulp, he employs 400 grammes 
(four-fifths of a pound) of oxalic acid, which has the double advantage of 
bleaching the colouring matter already oxidised, and of neutralising the 
alkaline principles which favour such oxidation ; he adds to the oxalic acid 
one pound, or a little more, of sulphate of alumina, entirely deprived of 
iron. The principal agent in this mode of bleaching is the oxalic acid, the 
